1. SMTP CS176A Ramya Raghavendra ramya@cs.ucsb.edu

2. SMTP • What is SMTP? • Simple Mail Transfer Protocol • SMTP server – every email client interfaces to send email • List of SMTP servers in transit - Check the headers on your email! • Why talk directly to SMTP server? • Automation of emails in applications • Without dependency on another email client • Real time notification of status • Wrong ID, passwords etc

3. Consider Windows alternative like MAPI More complex More overhead Example

4. Multipart Messages • But can we send multipart messages with attachments? • YES • SMTP is only a delivery mechanism, nothing to do with contents • RFCs on how to create multipart messages with attachments • Your assignment • Simple text

5. SMTP commands

6. For testing purposes • Part 1 : • Please note: NO TURNIN • Part 2: • To : command line argument • Subject: cs176aHW3ProgPart2 • Content: Name and Perm no.

7. Email Sender: Logic /* open the network connection */ sfd = smtpConnect(smtp_server,smtp_port); if (sfd == INVALID_SOCKET) { rc=(-1); goto cleanup; } // Send HELO smtpHelo(sfd,helo_domain); //Send “From” address smtpMailFrom(sfd,from); //Send “To” address smtpRcptTo(sfd);

8. Email Sender: Logic (Cont) //Send Data smtpData(sfd); //Send End-of-mail “.” smtpEom(sfd); //Send QUIT smtpQuit(sfd);

9. Connection to SMTP Server /* connect to SMTP server and returns the socket fd */ static SOCKET smtpConnect (char *smtp_server, int port) { SOCKET sfd; sfd=clientSocket(smtp_server,port); if (sfd == INVALID_SOCKET) { errorMsg("Could not connect to SMTP server \"%s\" at port %d\n", smtp_server,port); return (INVALID_SOCKET); } /* save it. we'll need it to clean up */ smtp_socket=sfd; return (sfd); }

10. One example /* SMTP: HELO */ static int smtpHelo(int sfd,char *helo_domain) { memset(buf,0,sizeof(buf)); (void) snprintf(buf,sizeof(buf)-1,"HELO %s\r\n",helo_domain); //Socket write function sockPuts(sfd,buf); return (smtpResponse(sfd)); }